• European Marine Science
• PL close
• Aquaculture close

Abstract In 2014 and 2016 in Poland a few disease outbreaks caused by Kocuria rhizophila and Micrococcus luteus were diagnosed in rainbow trout and brown trout. In each of these events, abnormal mortality (approximately 50%) was accompanied by pathological changes in external tissues and internal organs. Exophthalmia, swollen abdomen, increased skin melanisation as well as skin petechiae and focal lesions were often seen in moribund fish. In many fish inflammation of the intestine, liver congestion, and hemorrhages in the tail part of the muscles were also observed. Samples from moribund fish internal organs were inoculated onto blood agar and trypticase soya agar, and incubated for up to 3–4 days at a temperature of 27 °C. In the majority of cases uniform growth of bacterial colonies was observed; and sometimes these bacteria appeared in predominant numbers. The bacteria identifications were performed using standard kits (API 20 Staph and Vitek 2). Sequencing was carried out so as to improve the biochemical identification of isolated bacteria and the evolutionary relationships of their taxa. It was also conducted in order to find the possible source of the fish infection. Comparison of our strains' molecular structures with the data available in GenBank showed that Kocuria rhizophila or Micrococcus luteus had never been isolated from diseased fish before, and that our isolates were very similar to the strains which had been isolated from food processing environments (in the case of Kocuria rhizophila) and from scallops (Micrococcus luteus). The challenge tests performed with our strains of Kocuria and Micrococcus on rainbow trout in laboratory aquaria confirmed the three Koch postulates. Antibacterial disc diffusion studies showed that Kocuria rhizophila and Micrococcus luteus are sensitive to most of the drugs tested i.e. tetracyclines, β-lactams, a macrolide, and amphenicol. The results of these studies show that control of outbreaks of the diseases in rainbow trout or brown trout seems realistic if caused by Kocuria rhizophila or Micrococcus luteus.

Item does not contain fulltext 7 p.

Abstract: This paper examines how the traditional carp sector in Poland developed during the recent period, paying a particular attention to the different forms of innovations that have been implemented. Mostly based on first-hand, face-to-face interviews, the paper shows that despite the fact that aquaculture of carp is still characterised by strong traditional and cultural features, different categories of economic agents along the value-chain engaged in various kinds of technical, market and institutional innovations. These innovative strategies could be further replicated and developed through collaborative process, where policy makers have a potential role to play. The research results showed the existence of huge potential for innovation in traditional carp sector in Poland, especially in terms of alternative ways of marketing products for small and medium scale farms.

Abstract Domestication and selective breeding can mitigate current bottlenecks in European perch aquaculture. Monitoring the condition and stress tolerance of European perch stocks from different recirculating aquaculture systems is of general interest to set the baseline values of promising candidates for further breeding processes. We recorded morphometric, behavioural (critical swimming speed, activity, aggressiveness, propensity to approach a novel object), and physiological parameters (plasma cortisol, glucose, ion concentrations, enzyme activity levels) after stress induction across four European perch stocks obtained from different aquaculture facilities in France (I and II), Denmark, and Hungary. The European perch stock from Denmark revealed the population with the most pronounced activity pattern. This was reflected by the highest relative swimming speed and a high percentage of bold-exploratory behaviour, which coincides with increased aggressive interactions within this stock. Additionally, we detected a higher tolerance to adverse environmental challenges in the perch stock from Denmark compared with the stocks from France and Hungary. The observed characteristics suggest that the stock from Denmark has a higher potential in the future framework of selective-breeding assessment. Further in-depth research is required to elucidate which traits and genetic as well as epigenetic components accelerate the domestication processes of European perch aquaculture and promote selective breeding processes.

In this study, the systematic development of a protocol allowing an effective advanced spawning of wild Eurasian perch with the use of salmon gonadoliberin analogue (sGnRHa) was undertaken. The novel approach used in this study involved the application of a strategy of the repeated administration of sGnRHa (i.e., the hormone was given in two doses: priming and resolving) along with an additional thermal stimulation of ovulation. Additionally, the developed protocol was tested for its suitability in the controlled reproduction of domesticated broodstock. The obtained results suggested that the best interval between the hormonal treatments is 7 days when a water temperature of 10°C is kept constant between the two injections and when the resolving injection is followed by rapid increments of temperature up to 12°C, at which spawning is expected. This study revealed that the most suitable priming dose of sGnRHa was 10 µg kg-1 , at which the highest embryonic survival rates (>80%) and International audience

Introduction to the special issue on recent advances in fish gamete and embryo research